The present invention relates to a servoamplifier or a control circuit for automatically controlling the diaphragm of a camera for the proper exposure.
Heretofore, differential amplifiers or complementary amplifiers have been utilized in order to automatically set the diaphragm of a camera for the proper exposure. These circuits, however, normally require bridge connection thereby limiting the range of function due to the condition of the bridge connection. In case of utilizing a differential amplifier, for example, current always flows in the two coils of the driving motor of the diaphragm even though the diaphragm is set for the proper exposure at the balanced condition of the two coils, thereby making it impossible to avoid loss of energy of the electric source. Further, the input for the control circuit of the diaphragm is affected by the variation in the voltage of the electric source.